This invention relates to an improved coffee brewing machine and particularly to an improved system for heating water in such a machine and for other purposes.
Coffee brewing machines commonly known as automatic drip coffeemakers have achieved widespread popularity in recent years. In machines of this type, hot water passes through the coffee grounds a single time, and primarily for this reason, the coffee has a better flavor than is achieved with percolator type coffee pots. Even so, the coffeemakers presently available are unsatisfactory in many respects.
There are two general types of drip coffeemakers, one of which heats the water in a manner causing it to pass upwardly through a long tube. After exiting from the tube, the hot water flows to a spout which directs it into a basket filled with coffee grounds and then into a carafe or other vessel. A major problem with these devices is the tendency of minerals such as calcium to precipitate out of the hot water and collect in deposits which clog the tubes and other portions of the plumbing. Aside from impeding the flow of water through the machine and causing high pressure areas, the deposits restrict heat flow from the heat source to the water and cause inaccurate operation of the thermostatic switch which is usually provided. Therefore, substances such as vinegar must frequently be passed through the machine at regular intervals in order to break up and remove the mineral deposits. Adding to this problem is the inaccessibility of the tubes; the plumbing cannot be inspected to determine the extent to which deposits are present and/or the extent to which the vinegar has been effective in removing them.
The other general type of coffeemaker is commonly known as a flow through unit. Here, the water which is poured into the main reservoir drains slowly through a shallow tray or pan in metered amounts. In the pan is an electric heater so that the water is heated as it flows through the pan. The hot water is then directed through the grounds and into the carafe. Again, the problem of mineral deposits is encountered, although, in this case, the deposits develop in the pan and on the heater, both of which are inaccessible for inspection and cleaning. Safety problems are also encountered due to the need for a high wattage heating unit in order to apply heat to the water at the required rate.
Maximum flavor is extracted from coffee grounds when the water is as hot as possible at the time it encounters the grounds. However, in existing coffeemakers, it is typical for the water to travel a relatively long distance after it has been heated and before it passes through the grounds. Consequently, the water loses a substantial quantity of heat before it reaches the grounds, and the quality of the coffee brew suffers accordingly. Heat is also lost as the water passes through the spreader that is usually provided on top of the basket to spread the water over the grounds. Heat losses result from vaporization.
Some existing coffeemaking machines are further characterized by excessive cost and undue complexity, and by uneven distribution of water over the coffee grounds. The latter problem is particularly acute when less than the maximum amount of water is passed through the machine. The spreaders, if any, and baskets function as intended only at full capacity operation, and their effectiveness is inadequate with smaller amounts of water and coffee grounds. Smaller portions also provide less hot water.
The control systems for existing coffee brewing machines have also been less than satisfactory. Usually, a simple thermostat is provided to control the operation of the heating unit. In this type of control circuit, the heater is able to cycle on and off at frequent intervals as fluctuating temperatures are sensed by the thermostat. It is also common for dry cycling of the machine to occur due to inadvertent positioning of the on-off switch to the "off" condition in the absence of water.
There are a number of other situations in which liquids must be heated to a high temperature and then delivered into a container. For example, liquids must be heated in order to prepare beverages and foods such as tea, soup, and the like. Devices which have been developed for applications such as these suffer from many of the same problems and drawbacks as coffeemakers, particularly the buildup of mineral deposits which are not easily detected and removed.
It is an object of the present invention to provide an improved coffee brewing machine which has a simplified and economical plumbing system and which minimizes the problem of mineral deposits. In this respect, it is important to the invention that the hot water travels only a short path and that this path is readily accessible for visual inspection and for easy cleaning if mineral deposits are detected.
Another object of the invention is to provide an improved system for quickly heating water to a high temperature and delivering it to a container. The short path which the hot water travels is also significant in this regard because it minimizes heat losses, thus making the heating system useful in various types of devices such as coffeemakers and water heaters for tea, soup and the like.
It is still another object of the invention to provide, in a coffee brewing machine, an improved water spreader which minimizes heat losses via vaporization, while promptly and uniformly distributing hot water through the coffee grounds in a manner to evenly saturate them.
Yet another object of the invention is to provide, in a coffee brewing machine, an improved brewing basket for holding the coffee grounds.
A further object of the invention is to provide a coffee brewing machine which includes means for accurately controlling the water flow in accordance with the rate at which it is heated.
An additional object of the invention is to provide, in a coffee brewing machine of the character described, a reservoir that may be removed from the machine in order to receive water directly from a faucet or other source.
A still further object of the invention is to provide, in a coffee brewing machine of the character described, an improved control circuit which acts to prevent inadvertent dry operation and on and off cycling of the machine.
Yet another object of the invention is to provide a coffee brewing machine of the character described which functions effectively at full capacity and also at lesser capacities.
A further object of the invention is to provide a coffee brewing machine of the character described which is constructed simply and economically and which operates safely.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.